Co-showrunner Elwood Reid will run the second season of FX's "Bridge" on his own, while Stiehm heads back to the Showtime drama for the series' recently renewed fourth season as well as a not-yet-ordered fifth.

MeredithStiehm is headed back to the Homeland writers room.

Stiehm, a key member of the Showtime series' original writing staff, had left the CIA drama ahead of its third season to co-run FX's The Bridge with Elwood Reid. But in an unexpected twist, Stiehm is stepping down as the border drama moves forward with its second season. The Emmy-winning writer-producer has inked a deal with Homeland studio Fox 21 to return to the Homeland room for the series' fourth and, pending an order, fifth season as an executive producer.

"We're thrilled to welcome Meredith back, as she's been an integral part of Homeland from the beginning," said Fox 21 president Bert Salke, adding: "She's a fantastic writer and this deal returns her to this hugely valuable asset as well as allows us to develop with her down the road."

According to multiple sources, Stiehm and Reid --who had worked together on her long-running CBS procedural Cold Case -- didn't see eye to eye on the direction of the series starring Diane Kruger and Demian Bichir. Reid will become the sole showrunner of the FX show, while Stiehm maintains her executive producer credit. In its first season with Stiehm, Bridge proved a solid performer for FX, tracking just shy of The Americans. In late September, it was granted a 13-episode second season, which is expected to premiere in the summer of 2014.

Though a showrunner shake-up is rarely ideal, the move proves advantageous for the staff of Homeland, led by showrunner Alex Gansa. Stiehm, who was part of the initial six-member staff that was widely dubbed a "murderers row," had been the only female voice in the room for the show's first two seasons. (Judging Amy's Barbara Hall was brought aboard in Stiehm's absence.) As such, she was particularly hands-on in writing for the show's lead, Carrie Mathison (Claire Danes), and brought personal experience (through her sister) to the character's bi-polar storyline. In her two-season tenure with the Emmy-winning series, Stiehm penned some of the drama's most acclaimed episodes, including season one's "The Weekend" (where Carrie and Damian Lewis' Brody go to her cabin) and, with Gansa, the season-two finale, "The Choice."

Eager to have her back in the fold, Gansa already enlisted Stiehm to co-write the series' third-season finale, which is set to air Dec. 15. She is repped by WME and Felker Toczek.